Definition of "monicker"

"Kid, you've outgrown 'Young Blood' as a monicker".

1969, Iceberg Slim, Pimp: The Story of My Life, Holloway House Publishing

"I was given the monicker in med school, because my name was John and I did a certain amount of night-tripping."

2011, James Ellroy, L.A. Noir: The Lloyd Hopkins Trilogy, Random House, page 407